Belgium developing SMRs

The lastest energy-related action of the Belgian government is
to provide the money that was promised to SCK to evaluate or co-develop SMR technology. This is a side effect of the negociations with ENGIE in a desperate attempt to re-open a few NPPs to keep the light on.

This is politics. While SCK wonders if the money really there, the government does not agree to the SCK partnerships. These partnerships end the illusion that Belgian is still a forerunner in nuclear technology.

One can also wonder if there is a result obligation, with defined milestones, other than paper-ware, to motivate the money-gobbling Class-1 facility?

But that’s politics. Let’s consider the SMR motivation in more detail.

The term “SMR” covers a vast spectrum of nuclear reactor designs, ranging from LWR to MSR. The only common denominator is that they are “small”, meaning they are capable of a thermal power level of 100 to 300 MW.

They are called safe mainly because the low power level allows passive cooling of the decay heat after an accidental shut down. This is a false argument because the big Gen-III reactor designs (e.g. Westinghouse AP1000) also allow that.

They should be cheaper because they could be factory produced instead of build on-site. Again a false argument, coined by a.o. BG, believing that NPP’s can be shipped like smart phones. Seen any of his phones, lately?

They are called financially realistic because the investment per unit is smaller. However, in the end, one still has to pay for all required installed power one way or another. Scale benefits are a thing, really.

How can SMRs ever be proliferation resistant? In the current geopolitical context, even the old proliferation ideas need to be revisited. Installing a bunch of SMRs together on one secure site just shifts the problem.

And then there is physics. This is where it gets really interesting.

In a chemical reactor, the density of the reagentia determines the production. It gets more complex in a nuclear reactor: there is a stringent constraint between the density of the reagentia and the size and shape of the reactor.
In a nuclear reactor, the reagentia are target nuclides on the one hand, and neutrons on the other hand. But unlike in a chemical reactor, you cannot just pour in these neutron reagentia. Instead, they have to be created inside the reactor, and more in particular just before they are used.

Indeed, neutrons are spooky particles that fly out of the reactor incredibly fast, unless they meet a suitable nucleus on the way out, with which they can actually react. This means that the nuclei density must be sufficient to prevent neutrons to leave the reactor and fly off into space as useless particles. So if you want the reactions to be sustainable, the size and the shape of the reactor and the density of the fuel have to be precisely in equilibrium. This means that an SMR needs denser fuel. The smaller the reactor, the denser the fuel needs to be. For a uranium fuelled SMR, this means higher enrichment. And then you bump into the proliferation laws.

Making a reactor smaller comes with a severe cost, and there is a limit, too.

That is why SMR are a hoax.